Rethinking the Commodore 64 Memory Map (2018) (opens in new tab)

I think the general idea that the VICII could use a range of addresses for one thing while the CPU used it for another was understood from the start.

But I would guess the sheer inventiveness & range of things people put the C64 to was/is astonishing, even to the wildest thinker on the development team.

Complete side note: The brain is a very strange thing. I read this post earlier and then started to so some work. I repeatedly found myself trying to type a double quote using SHIFT-2, which is the key combo for the PET and C64 (my first computers). Actually on the PET, it's not the 2 key, but the key where the 2 would be on a modern keyboard.

Weird the way 30+ year old muscle memory is invoked.

Perhaps, but it is more likely they provided many options, hoping it worked out.

Sometimes it did not. We look back, and some machines were almost there, like the Apple GS. Still great, but with just a bit more thought, could have been amazing.

Many of the better effects on C64, and other computers, were actually exploits. Bugs in the logic were found, then abused, then perfected.

Most of the better titles on the old 2600 (VCS), for example, exceeded engineering specs. A bit of flexibility left in turned out to make all the difference in the world.

Older machines used a combination of software and hardware. That combination turns out to be quite potent over time as people continue to explore what may be possible.

Some have coaxed better color, interlaced video, and more out of a C64, despite that not being intended.

The memory map options were likely flexible, "just in case", and where that was the thinking back then, it often became the max potential case.

I am pretty sure you can find similar tales of squeezing every single available byte out of the c64 in programmer diaries from the eighties. Bank-switching the VIC and SID out and dumping rarely-changing data like character sets into the space normally used for their I/O registers was not uncommon back then.

The minor gridlines are dotted. The "tiny o's" appear where the spaces of two lines are aligned, so four dots appear around the crossing point.

C64os is by Greg Nacu from the Toronto area. It's a hobby project along with a portable c64 he's built that's more portable than an SX-64 and much more versatile due to modern components.